Tractor shovel-fast lowering

ABSTRACT

A tractor shovel having a pair of actuators for raising the shovel, and power down means for lowering it in an arrangement in which the power (hydraulic fluid) is applied to only one of the actuators so that the shovel is lowered at a faster rate than if the same quantity of fluid were applied to both the actuators.

O United States Patent [15] 3,638,81 8

Kin 51 Feb. 1 1972 [54] TRACTOR SHOVEL-FAST LOWERING 3,481,251 12/1969 Shook ..214/138 [72] Inventor: James E King, Cupemno Calif 2,628,731 2/1953 Reuter ..2l4/762 [73] Assignee: Clark Equipment Company Primary Examiner-Gerald M. Forlenza [22] Filed: Apr. 22 1970 Assistant ExaminerJohn Mannix [2 1 A l N 30 740 Attorney-Paul H. Gallagher [57] ABSTRACT [52] U.S.C| ..214/762 A tractor shovel having a pair of actuators for raising the [51] 11. Cl. 1 1 B66f 9/00 Shovel, and power down means for lowering it in an arrange [58] Field of Search ..214/140, 138, 762, 778 mam in which the power h d li fl id) i applied to only R i cted one of the actuators so that the shovel is lowered at a faster e erences I rate than if the same quantity of fluid were applied to both the UNITED STATES PATENTS actuators- 3,l05,603 10/1963 Beyerstedt et a1, ..2l4/762 1 Claims, 8 Drawing Figures PATENTED FEB 1 I872 SHEEY 10F INVENTOR JAMES F. KING ATTORNEY PATENTEU FEB 1 I972 SHEET 2 0F &

FIG. 3

FIG. 4A

ATTORNEY PATENTED FEB I972 SHEET 30F FIG. 48

FIG. 4c

INVENTOR JAMES F. KING ATTORNEY TRACTOR SI-IOVEL-FAST LOWERING Field of the Invention The invention resides in the general field of tractor shovels in which a shovel is mounted on boom arms pivoted on the tractor, and a pair of actuators such as hydraulic cylinderpiston devices are utilized for raising the boom arms, and the shovel. Heretofore it has been quite customary that to lower the shovel the power applied to the actuators was merely released and the shovel was permitted to float down under its own weight, with consequent great time consumption. However in the past it has also been customary at least at times to utilize power down in the operation, but the power, or the hydraulic fluid, was applied to both or all of the actuators, and while in those cases the shovel was lowered faster than if it merely floated down, its lowering was not as fast as if the power were applied as in the present invention.

OBJECTS OF THE INVENTION A broad object of the invention is to provide a novel arrangement for overcoming the disadvantages attendant upon slow lowering of a tractor shovel of the general kind heretofore known and as referred to above.

Another broad object is to provide in a tractor shovel having a plurality of actuators for raising the shovel, means for applying all of the power available to less than all of the actuators in a power down operation whereby to increase the'speed of lowering.

An additional and more specific object is to provide a tractor shovel which incorporates a plurality of actuators, such as two, for raising the shovel, and in which power means is provided for imposing a certain maximum power to the actuators for raising the shovel, consistent with relatively great loads encountered which are to be carried by the shovel, and in which that same maximum power can be utilized on less than all of the actuators, such as on only one, for lowering the shovel whereby since the total maximum power is applied to only one of the actuators, the shovel is lowered at a much greater rate than if it were applied to all of the actuators.

A further object is to provide a tractor shovel of the foregoing general character which includes means selectively operable for providing a power down operation and floating condition when the shovel reaches the ground, so that the shovel then floats thereon.

A still further object is to provide a novel method of applying power in a tractor shovel wherein the maximum power utilized for raising the shovel in a mechanical advantage is utilized for lowering the shovel at lesser mechanical advantage but at a faster rate.

DESCRIPTION OF A PREFERRED EMBODIMENT In the drawings:

FIG. 1 is a perspective view of a tractor shovel embodying the features of the present invention;

FIG. 2 is a side view, showing only a portion of the tractor itself, and with the shovel at ground level in full lines and in two alternate positions in dot-dash lines;

FIG. 3 is a diagrammatic view of the actuators for the shovel and the valve means for controlling them; and

FIG. 4 is a series of diagrammatic indications, individually identified A to E, representing the positions of the actuators for the shovel, and of the valve means, in each of the different positions or attitudes of the device of the invention.

Referring in detail to the accompanying drawings, attention is directed first to FIGS. 1 and 2 showing the tractor shovel of the present invention in its entirety. In this view the tractor or carrier vehicle itself is indicated at and a shovel or loader component indicated in its entirety at 12, which in its broad aspects is of known character. The shovel component 12 includes a shovel proper 14 mounted on a transverse axis 16 in a pair of boom arms 18 which are pivotally mounted on opposite sides of the tractor 10, on a transverse axis 20. The boom arms are raised and lowered by, and under control of, a

pair of power transmitting actuators or jacks 22 which in themselves may be of conventional construction; these actuators are preferably double-acting hydraulic cylinder-piston devices and are pivotally connected at one end on an axis 24 on the tractor and on a transverse axis 26 on respective ones of the boom anns 18. The actuators 22 are individually identified as 22R and 22L (for right and left) for convenience in the description of their functions. As indicated above, both are utilized in raising the shovel, but only one is utilized in lowering it, and the right one, 22R, is arbitrarily selected as the lowering one (FIGS. 3 and 4). This one (22R) may also be designated the main one, and the other one (22L) the secondary one.

Each actuator 22 includes a cylinder 28 and a piston 30 having a piston rod 32 extending therefrom, the cylinder being mounted to the tractor (FIGS. 1 and 2) and the piston rod to the respective boom arm. The actuators are mounted in a recognized manner as having their head ends lowermost and their piston ends uppermost. In each actuator the piston forms a relatively large cavity, or extension chamber, 34 on one side, at the head end (FIGS. 3 and 4), and another cavity, or contraction chamber, 36 on the other side, at the piston end, which is of lesser capacity because of the presence of the piston rod 32.

FIG. 3 is a diagrammatic illustration of the arrangement of the actuators 22 and main control valve means 38. The valve means 38 may be of any desired known type such as an open center type valve, and it includes manually actuatable elements 40. The arrangement includes a power means 42 such as a hydraulic pump from the outlet of which a line 44 leads to the valve means 38. Leading from the valve means is one line 46 having one branch 46R communicating with the chamber 36 of the power down actuator 22R, and another branch 46L communicating with an individually controlled valve 47 which is pilot operated and receives control signals through a branch line 46A. The valve 47 is self biased to the position shown in FIG. 3 as by a spring in a known manner, and is shifted to the position of FIG. 4D in an operational step referred to below. When in the position of FIG. 3, it acts to connect the chamber 36 of the actuator 22L, through a line 49 with a line 50 leading to a reservoir 52, an element 52A thereof being shown diagrammatically adjacent that position. Another line 48 communicates with the exit side of the valve means 38 and has a branch 48R leading to the chamber 34 of the actuator 22R and another branch 481. leading to the chamber 34 of the actuator 22L. Additionally another line 54 leads from the valve means 38 to the reservoir 52, an element 528 thereof being shown diagrammatically adjacent that position, and from the latter a line 58 leads to the intake of the power means or pump 42.

The valve means 38 is of known kind, manually controlled as well as automatically controlled such as in response to pressure, position of the moving elements, etc. The specific detail structure of the valve means may be as desired for the purpose of carrying out the functions hereinafter referred to.

In accordance with a principal object of the invention, it is desired to apply power to the shovel in the lifting movements in a manner to utilize great mechanical advantage, i.e., in the case of hydraulic cylinders, a given quantity of hydraulic fluid is applied at a given rate of flow to a plurality of actuators for raising the shovel so as to provide a great reaction surface (total piston area) for maximum power; in the lowering movements, that same quantity of hydraulic fluid is applied to a lesser reaction surface (lesser total piston area) but at the same linear or quantitative rate of flow, so that the shovel is lowered at a greatly increased rate. Specifically this is done by applying a given quantity of hydraulic fluid at a predetermined rate of flow, to two cylinders in the raising movement, the applying the same quantity of hydraulic fluid at the same rate of flow, to only one of the cylinders in the lowering movements, whereby the displacement of the one cylinder in the lowering movement is equivalent to the cumulative linear displacement in two cylinders in the raising movement. In the case of the one cylinder, the rate of movement is at least twice as great, but actually that rate is more than twice as great because the cavity in the cylinder at the piston end, in which the fluid is introduced in the lowering movements, is less than on the other side.

Referring to FIG. 4, the individual views A to E inclusive show positions of elements and relations therebetween, as well as indications of direction of movement of the elements and flow of the hydraulic fluid. In these views, the valve 38 is represented diagrammatically according to individual functions to be performed in the respective positions in those views.

FIG. 4A shows the valve 38 in a beginning position to which it may be manually set by means of the elements 40 (FIG. 3); in this position the hydraulic fluid is pumped by the pump 42 through the line 44 and through the valve 38, to the line 48 and the branches 48R, 48L, thereof into the chambers 34 of the actuators. In this step both actuators are operated and utilized in raising the shovel. In this operation, because of the setting of the valve 47 as in FIG. 4A, the fluid from the chamber 36 in the actuator 22L is vented through the line 50 to the reservoir 52 without performing a working function. In this same operation the fluid from the chamber 36 in the other actuator is vented through the line 46R, valve means 38 and the line 54 to the reservoir 52. After the shovel is raised to the desired height, it is held there, by setting the valve 38 in a corresponding position (FIG. 4B), as by a spring release, or sequence spool, operation function. The lines 46, 48 are shut off and the lines 44, 45 are interconnected to form a closed circuit through the pump. In this state of equilibrium the load in the shovel is dumped by suitable means (not shown herein).

FIG. 4C shows the condition of the hydraulic circuit in a power down operation in which the power is applied to only one of the actuators in accordance with a principal feature of the invention. To perform this step the valve 38 is manually shifted to the position shown in this figure in which the lines 44, 46 are connected and the lines 54, 48 are similarly connected. In this condition of the hydraulic circuit, the valve 47 remains in the same position as above described and the branch line 46L is closed therein. Accordingly, all of the fluid in the line 46 is directed through the branch line 46R and into the one actuator 22R, and since all of the fluid pumped is directed into one actuator, that actuator moves at a greater rate, and more than twice the rate, than in the raising movement, as referred to above. The chamber 36 in the other actuator 22L remains vented through the line 50 to the reservoir and the fluid in the reservoir flows into that chamber, it being understood that the lowering movement of the shovel forces the piston 30 down in the actuator 22L. The fluid in the chambers 34 of both actuators returns through the branches 48R, 48L and the line 48 in return to the reservoir.

It is contemplated to be within the compass of the invention that the actuator or cylinder 22L be vented to atmosphere at its chamber 36, i.e., devoid of hydraulic fluid, and in such situation the raising movements would be accomplished in the same manner. However this would not be a preferred arrangement because of lack of an advantage described in the following paragraph.

The construction of the invention is also applicable to applying power to both of the actuators in a power down operation, such for example in the case where a particularly heavy load or operation is encountered. For example, in handling a highly resistant load such as rock or hard ground, the operator would hold the valve 38 in the usual power down position (FIG. 4C) when the shovel hits the ground, and the pressure differential developed, as between the line 46A and the biasing means in the valve 47, shifts that valve to the position of FIG. 4D, establishing communication between the branch line 46L and the chamber 36 of the secondary actuator 22L. The valve 47 is of known operational characteristics so as to respond in the manner stated in response to such pressure. Notwithstanding this possibility, in a normal operation the pressure developed in this one actuator 22R as described in connection with FIG. 4C IS sufficient to drive the shovel down,

and is actually sufficient to raise the front end of the vehicle off of the ground in reaction to the shovel so engaging the ground.

FIG. 4E shows the condition of the hydraulic circuit for floating. To produce this condition the valve 38 is manually shifted to the position shown namely, interconnecting all of the lines 44, 46, 48, 54 through a bypass line 60, and in this condition the valve 47 remains as represented, namely the same position as shown in FIGS. 4A, 4B and 4C, and the chambers on both sides of the piston in the main actuator 22R are freely connected in an unrestricted circuit, while in the case of the secondary actuator 22L the chamber 34 is connected in that same circuit and the chamber 36 is vented to the reservoir 52. Accordingly, the shovel will float on the ground and follow the contour thereof, and of course if the circuit should be shifted to the position shown in FIG. 4E while the shovel is raised, the shovel will float down by gravity.

Iclaim:

1. A tractor shovel construction comprising a mobile vehicle, a shovel, boom arms pivoted on the vehicle for vertical swinging movements and supporting the shovel at their extended ends, hydraulic power means, a pair of hydraulic actuators mounted on the vehicle and operatively connected with the boom arms for raising and lowering the latter in response to extension and contraction of the actuators, the actuators having extension and contraction chambers, power transmitting means operatively interconnecting the power means and the actuators including:

a hydraulic circuit,

a manually operated control valve in the hydraulic circuit for controlling the flow of hydraulic fluid in opposite directions between the power means and the actuators,

a first line in the circuit communicating between the control valve and the extension chambers of both the actuators,

a second line in the circuit leading from the control valve and having a first branch communicating with the contraction chamber of a first of the actuators and a second branch capable of communication with the contraction chamber of the second of the actuators,

a second valve in the second branch self-biased to a first position in which it blocks communication of the second branch with the second actuator and movable to a second position in which it establishes such communication,

a pressure line operatively interconnecting the second line and the second valve whereby the hydraulic fluid in the pressure line upon reaching a predetermined pressure moves the second valve to its second position. 

1. A tractor shovel construction comprising a mobile vehicle, a shovel, boom arms pivoted on the vehicle for vertical swinging movements and supporting the shovel at their extended ends, hydraulic power means, a pair of hydraulic actuators mounted on the vehicle and operatively connected with the boom arms for raising and lowering the latter in response to extension and contraction of the actuators, the actuators having extension and contraction chambers, power transmitting means operatively interconnecting the power means and the actuators including: a hydraulic circuit, a manually operated control valve in the hydraulic circuit for controlling the flow of hydraulic fluid in opposite directions between the power means and the actuators, a first line in the circuit communicating between the control valve and the extension chambers of both the actuators, a second line in the circuit leading from the control valve and having a first branch communicating with the contraction chamber of a first of the actuators and a second branch capable of communication with the contraction chamber of the second of the actuators, a second valve in the second branch self-biased to a first position in which it blocks communication of the second branch with the second actuator and movable to a second position in which it establishes such communication, a pressure line operatively interconnecting the second line and the second valve whereby the hydraulic fluid in the pressure line upon reaching a predetermined pressure moves the second valve to its second position. 